Magnetic inspection apparatus



March 2, 1948. T. DE FOREST MAGNETIC INSFEQTION APPARATUS Filed July 22, 1942 v 742%6/ defa/QSZ Patented Mar. 2, 1948 Taber dc Forest,

flux Corporation, Delaware Chicago, 111., assignor to Magna- Ghicago, 111., a corporation of Application July 22, 1942, Serial No. 451,851

magnetizable metal objects for flaws and defects. The paramagnetic powder may be applied to the magnetized object in a dry state or the paramagnetic powder may be carried in suspension in liquid, such as a light oil, and either sprayed over the object or applied to the object in the form of 9. bath.

The above invention relates to a novel means for applying paramagnetic powder to a magnetized object in a dry state. More particularly, it is an object of the present invention to provide a novel means for delivering'and applying the powder at very low velocity.

It is a further object of the present invention to provide a novel means for applying paramagnetic powder to a magnetized object in which the powder is borne in' a light cloud at low velocity and in which agaseous fluid, such as air, acts as a suspensoid.

Another and further'oblect of the present invention is to provide a novel means of first applying dry paramagnetic powder to a magnetized object and thereafter applying a light blast of gaseous fluid, such as air, to blow away the excess powder.

Another and still'further object of the present invention is to provide a novel powder blower unit including a powder gun having an air noz- 'zle, an air and powder nozzle, and a light therein for illuminating the ,work.

Still another and further object o the present invention is to provide a novel powder, blower unit having novel means therein for eifecting a fine suspenson of paramagnetic powder in a low velocity stream of air.

The-novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims. My invention itself, however, both as to its organization,

manner of construction and method of operation, together with further objects and advantages thereof, may .best be understood by reference to 4 claims. (or. -183) g the following description, taken in connection with the accompanying drawing, in which the single figure thereof illustrates diagrammatically a powder blower unit which is an embodiment of the present invention.

The powder blower unit as illustrated in the drawing includes a powder blower i0 and a powder gun II. The powder blower ill, in general, comprises a closed hopper l2 which is initially filled with paramagnetic powder, an air compressor l3 and a motor l4.

The hopper I2 is preferably V-shaped in cross section including downwardly and inwardly converging side walls I! a bottom wall it and a top cover member ll.

Disposed within the the lower mouth of the hood being of such dimensions as to extend over almost but not quite to the side walls [5 of the hopper i2. The hood i8 is preferably of conical shape and is connected I at its upper end to a conduit or hose is.

A compressor I3 is mounted below the hopper l2 and is driven by the motor it through a suitable coupling 20. The compressor i3 is connected through a two-way valve 2| to the hopper l2 and to an air tank 22. More specifically, the two-way valve 2| is connected to a conduit 23 which enters the hopper l2 through the base wall [6. The valve 2! is also connected to a conduit 24 to the air tank 22, which in turn is connected to a conduit or hose 25 which extends out to the powder gun i I; The valve 2| has a valving member 28 which is arranged to be moved between the full line position, as shown in the drawing, and the dotted line position, as shown in the drawing. When in the full line position, as shown in the drawing, the member 26 has closed the conduit 23 and thus air under pressure is fed only tothe air tank 22 and to the hose 25. When the valve member 26 is moved to the dotted line position, as shown in the drawing, the conduit 24 is closed and the conduit 23 is open. Air under pressure is then fed to the hopper l2. This air under pressure forces some of the paramagnetic powder up into the hood i8 and thence into the hose IS. The pressure is so adjusted that the resulting air stream is of relatively low velocity. The arrangement of the hood l8 and the hopper in conjunction with the conduit 23 causes a fine cloud of paramagnetic powder to be formed in the air'stream which moves through the hose t9 and emerges from the powder gun I i.

The powder gun II has a pair of conduits and 28 passing therethrough towhich the hoses Z5 and I9. respectively, are connected. The powhopper I2 is a hood l8,

der gun II also has a light 23 mounted in the forward end thereof immediately below the con-. duit 21 and 28. The powder gun H has a handle portion 30 which provides a convenient grip, and ,is also provided with a trigger switch 3| which, when depressed, connects a conductor 32 to a conductor 33 which are in a valve operating control circuit presently to be described.

The valve member 26 of the valve 2| is arranged to be operated by a solenoid 34. A biasing spring 35 is connected to the valve member 26 in such a manner that the valve m mber 28 is normally h ld in its full line position. as shown in the drawing. The valve member 26 is arranged to be moved to its dotted line position when the solenoid 34 is energized against the action of the biasing s r ng 35. (It is. of course. to be understood that the representations in the drawing of the biasing sprin 35 and the solenoid 34 are merely diagrammatic.)

The unitis arranged to be electrically conn cted to a suitab e source of alternating current through a plug 36. The plug 36 also preferably has a round connect on 31 which enables the powder blower casing to be grounded by a conductor-3R. The plug 36 is attached to conductors 39 and 44 which are connected to the primary windin 4| of a transform r 42through a switch 43. The'secondary 44 of the transformer 42 is connected through a pair of conductors 45 and 4 to the lamp 99. The transformer 42 is preferably a step-down transformer to enable the lamp 2!! to be ner ized bv a six volt su ly. It will be und r tood that whenever the switch 43 is closed the lam "is lit. The motor I4 is connected in para lel with the primary 4|. of the transformer 42 throu h conductors 41 and 48, and hence is connected directly to the power source when the switch 43 is closed. The control circuit of the valve 2| is connected in parallel with the motor I4 through a conductor 43 on one side and through conductors so. 33, trigger switch 3| and conductor 32 on the other side. i

To operate the powder blower unit the plug 38 is plugged into a suitable source of alternating current power such. for example, asasource 110 volt, 60 cvcle. single phase alternating current. The switch 43 is then closed. The motor l4 and the light 29, are both energized when the switch 43 is closed. Energization of the motor i4 causes operation of the compressor and since the biasing spring 35 is holding the valve member 28 in the position as shown by the full line in the drawing, air under pressure is fed through conduit 24,

air tank 22, conduit 23, and conduit 21 of the to the dotted line position as shown in the drawing, which causes air under pressure to pass into the hopper l2. This air under pressure emerging from the conduit 23 in the lower portion of the hopper l2 forces some of the paramagnetic particles in the hopper 12 up into the hood l8. The paramagnetic particles thus forced up into the hood l8 are carried in the form of a fine cloud in the air stream which is flowing out through the hose I9 and then through the conduit 21 of the powder gun Ii. It will be noted that due to' the fact that the hopper is entirely closed and it due to the fact that air under pressure is being fed into the hopper through the conduit 23 from the compressor l3. The air which acts as a suspensoid for the fine paramagnetic particles is then directed over the magnetized object to be tested by directing the muzzle of the powder gun H at the portion of the magnetized object to which the powder is to be applied. Due to the fact that the light 29 is carried in the muzzle of the powder gun II, it will readily be apparent that the portion of the object to which the powder is being supplied is illuminated during this operation.

After the paramagnetic powder has been deposited on the magnetized object the trigger switch is released to open the energizing circuit of the solenoid 34. A stream of air now emerges from the muzzle of the powder gun II in the place of a stream of air having paramagnetic powder suspended therein. This is directed over the portion of the magnetized object to which the powder has been applied. This blows oil? all oi. the paramagnetic particles previously deposited on the ob ect with the exception of those particles which have congregated over defects or flaws in the magnetized article. The particles over the defect or flaw are retained on the object due to the fact that there is an increase in flux 7 density at this point.

From the foregoing description it will be apparent that a very simple and efllcient method and means is provided by the present invention for applyingparamagnetic powder in a dry state to a magnetized object which is to be tested for flaws or defects and which readily and conveniently removes excess powder or powder which is not concentrated over defects on the magnetized object. It will further be observed that a novel method and means is provided for causing a fine suspension of paramagnetic particles in an air stream in which the air forms a suspensoid for the particles.

While I have shown. a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto, since many modiflcationsmay be made, and I, therefore, contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

I claim as my invention:

1. Apparatus for testing a magnetized object for flaws and other defects comprising a closed hopper having paramagnetic powder therein, a hood in said hopper diverging downwardly a conduit communicating with the upper part of said hood and extending out of said hopper, an air compressor, a powder gun, said powder gun having a pair of conduits therein and extending out through the muzzle of said gun, one of said conduits in said gun being connected to the conduit in communication with the hood and the other of said conduits in said gun being connected to said air compressor, said air compressor also having a discharge condiiit extending into the lower part of said hopper, and valve means in the discharge of said air compressor for selectively directing air to said hopper or directly to said gun.

2. Apparatus for testing a magnetized object for flaws and other defects comprisin a closed hopper having paramagnetic powder therein, a powder gun having a pair of muzzles, a compressor, means for selectively connecting the discharge side of said compressor to one of said muzzles and to said hopper, and conduit means extending between said hopper and the other of said sealed that a stream of air will result in the 1.1056 mu zl to said hopper and to one of said muzzies, a two- 'of said ducts being arranged to receive the others Apparatus for testing magnetized objects for flaws and other defects comprising a closed hopper having paramagnetic powder therein, a powder gun having a pair of muzzles and a trigger operated switch, a compressor, conduit means 5 connecting the discharge side of said compressor way valve in said conduit means for selectively controlling the passage of air from said compressor to said hopper and to said one of said 10 muzzies, selectively operable meansincluding said' Number trigger switch for controlling the operation or said at 19,511 two way valve, and conduit means extending be- 699,405 tween said hopper and the other of said muzzles. I I 783,218 4. In apparatus for testing magnetized objects 15 925,412 for flaws and other defects including means I 1 1,239,075 selectively supplying one of two streams of air, 1,372,058 one of the streams having paramagnetic powder 2,257,736 in suspension, the subcombination comprising a 2,335,11 powder gun having a muzzle with a pair of air '59 ducts therein, one of said ducts being arranged to receive one of said streams of air and the other gn bs 0! said streams of air, and means on said gun for selectively controlling the flow 01. said streams through said ducts.

TABER DE FOREST.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Name Date De Forest June 8, 1935 Newhouse May 6, 1902- Murray Feb. 21, 1905 Addie June 15, 1909 Bagnall et al Sept. 4, 1917 Bramsen et a1. Aug. 16, 1932 Ferrier Oct. 7, 1941 Hansen Nov 23, 1943 FOREIGN PATENTS Country Date Great Britain Apr. 10, 1930 

